Hook collector and method of producing same



May 27, 1958 R. L. LoNGlNl HOOK COLLECTOR AND METHOD OF PRODUOING SAME 3 Sheets-Sheet 1 Filed Sept. 4, 1953 mm/ mZ y m/m ,m M a M Y B 4.

May 27, 1958 R.L.LoNG|N| 2,836,521

HOOK COLLECTOR ANU METHOD 0F PRODUCING SAME Filed Sept. 4. 1953 3 Sheets-Sheet 2 ,za-' j/ IN V EN TOR.

Mrz-okfly May 27, 1958 R. l.. LoNGlNl 2,836,521

HOOK COLLECTOR AND METHOD OF PRODUCING SAME Filed Sept. 4, 1953 3 Sheets-Sheet 5 f7 7 ff 5 7q` i l J0 f/ f@ J7 /14 I x\\/\ l\ [l 7" J6 United States HOOK COLLECTGR AND lt/IETHGD F PRODUCNG SAM'E Application September 4, 1953, Serial No. 37 8,567

7 Claims. (Cl. '14S-1.5)

This invention relates to the class of electrical devices, such as transistors and rectiers, which utilize semi-conductive materials.

In the transistor art the part of a transistor to which the output lead is connected is called the coliectorf A particular type of collector is known as a hook` collector because of a certain hook in the curve representing the distribution of potential -in the transistor body. The presence of the hook produces a transistor that amplies current.

The present invention provides an improved hook collector in which the width of the region which causes the hool can be precisely controlled in both thickness and conductivity and may be made extremely thin so that the current amplification of the resultingdevice may be quite large.

The invention also includes a method of producing the improved hook collector.

in addition, the invention includes new combinations of components to produce new and highly desirable characteristics in the resulting devices.

These, and other objects and advantages ofthe invention will become apparent as the description proceeds.

In the drawings,

Fig. 1 is a diagrammatic cross section illustrating the method of the invention.

Fig. 2 is a view similar to Fig. 1, but showing the different layers resulting from diiusion.

Fig. 3 is a view similar to Fig. 2 but showing a completed transistor.

Fig. 4 is a diagrammatic cross section illustrating a different type of transistor.

Fig. 5 is a diagrammatic plan view of the device of Fig. 4.

Fig. 6 is a perspective view-illustrating another type of l transistor.

Fig. 7 is a diagrammatic fragmentary cross section of the device of Fig. 6.

Fig. 8 is a diagrammatic cross section of another type of transistor. Y

Fig. 9 is a diagram illustrating a known type of semiconductor rectifier.

Pig. l0 is a view showing the application of the present invention to the device offFig. 9.

Fig. 11 is a diagram illustrating another form of transistor device using the present invention.

A specic illustrative example will 'first be described.

To form a hook collector having a P-type base region I rst provide a body itl of germanium which has been doped with one of the P-type4 impurities, such as indium, to produce a body having the desired P-type conductivity. This 'P-type body will form the base of the resulting transistor.

i also provide a pellet 11 of an -alloy containing about 0.1% arsenic, 'balance'indium- Arsenic is'an N-type impurity having a fast rate of diffusion, `whileindium is a P-type impurityhaving a siower rate'of diffusion.

arent The pellet of indium-arsenic alloy is placed on the body of P-type germanium and the assembly is heated to about 570 C. to cause the indium-arsenic pellet to melt and to alloy with the germanium body. Some germanium dissolves in the molten pellet. The unit isthen cooled slowly (i. e. over a period of 5 min.) to approximately 55()o C.

During this cooling from 570 C. to 550 C. it is preferred to maintain the main body 1l!) of germanium cooler than the liquid alloy, as disclosed in co-pending patent application Ser. No. 374,547, tiled August 17, 1953. This gradient cooling results in a favorable redeposition of germanium from the molten alloy onto the main body 3 0 of germanium. However, insome cases this drop in temperature may be omitted, as other advantageous features of the invention may be used without this feature.

The assembly is now held at the 550 C. temperature for a diffusionperiod of from one-,half to one hour.

During the diffusion period the indium and arsenic both dilfuse into the germanium, as indicated diagrammatically by the arrows in Fig. 1. Due to its slower rate of diffusion the indium does not penetrate as far as the arsenic, and due to the higher percentage of indium in the pellet l1, the percentage of indium will be higher in the rst diifusion layer, which is the layer formed immediately .adjacent to the pellet il. .This dense indium diffusion is indicated by the heavy arrows in Fig. l.

Meanwhile, the arsenic, with its faster diffusion rate, has diffused farther into the germanium, and forms a second diusion layer extending beyond the first diusion layer. However, since only a small percentage of arsenic is present in the alloy pellet l1, the concentration of arsenic in rthis second diffusion layer is not very great. The arsenic diffusion is indicated by the light arrows in Fig. 1.

At the end of the diffusion period the assembly is cooled to room temperature.

The condition ofthe assembly after the diffusion period is indicated diagrammatically in Fig. 2, which shows that the button 11 of indium-arsenic alloy is alloyed to the body i0 by the following intermediate layers:

A layer 12 ofredeposited germanium, which contains some indium and arsenic;

A 1st dilfusion layer 13, which contains a small percentage of arsenic with a relatively much larger percentage of indium. Theamount of indium present in this layer must be enough to overcome the influence of the arsenic and to cause this layer to have P-type character; and

A 2nd diffusion layer id in which the concentration of arsenic is greater than that of indium, and since arsenic is an N-type material this layer is converted to N-typc material.

Since the diiferent diffusion rates of indium and arsenic are known, the time and temperature of the diffusion period can be chosen so as to produce a very thin and uniform 2nd didusion layer, which is an important factor in producing the improved hook collector.

To form a completed transistor from the assembly of Fig. 2 any suitable emitter may 'be added. Thus, Fig. 3 shows the assembly completed by alloying to the cpposite -side of body l0 a button 'i5 of any prefer-red N- type material. In this case the button 15 forms emitter, the original body 113 Vforms the base, and the layers 13 and .i4 form the hook collector.

In the above vdescription certain preferred materials have been mentioned in order to give concrete examples. It should be understood that other materials having similar properties may be substituted within the principles now to ybe explained.

A. MAIN BODY HAVINGP-TYPE PROPERTES Materials for ma'z'n body For the main body 10, it is possible to use any suitable 'this case the main Constituent semi-conductive material having P-type properties; Thus the body maybe formed of germanium, of silicongermanium alloy as disclosed in co-pending application Ser. No. 375,416, iled August 20, 1953, o r` of silicon alone.

' Main constituent of alloy'pellez In the example given above 'the main constituent of the alloy pellet 1 1 vwas indium, the same P-type material used to dope the mainlbody 10. By analogy, any similar P- type material, suchas aluminum may beY used asV the main constituent of the alloy pellet.

It is also possible to use for the main constituent of the alloy pellet 11 any metal, such as lead, tin, or gold, which is relatively inert as an impurity inthe material of the main body` 10.

An important feature of Vthis inventionris the fact that the-.pellet 11 includes a slow-diffusing P- type material and a rapid-diffusing N-type material.

Slow-d ltsing P-type material l .l

' In the example given abovey the characteristics ofthe iirst diffusion Ilayer depend upon the fact that indium is a relatively slow-diusing P-type material. Another slowin Vthe pellet '11. Note that in the example given above the pellet V11 included 99.9% of indium.

On the other hand, gallium has -av-relativelyhigh `segregation coeiiicient, and a much smalleramountV of it can be used. Forexarnpleyif the main constituent of i pellet 11 ishlead, it is possible to use 1% of'gall-ium with 1/2% of arsenic.Y (See next section.)

Rapid-dijjrmrng N-ype material jin the'example given above the characteristics of the second diffusion layer depend upon the fact that arsenic is a relatively rapid-diffusing N-type material. Another rapid-diiiusing N-type material that may be used similarly is antimony. These two materials have approximately the same diffusion rates. VVLithium is another N- Y type material having a rapid rateV of diffusion. lts diffusion rate. in germanium is veryrapid, but'fin silicon of body 10, and a lead 18 is connected to the k10 represents the main -body of base, material.

The other constituent ofthe alloy pellet would be ,P- type material that diffuses faster than the N-type material in the pellet. One such fast-diffusing P-type material is'copper, which diifuses quite rapidly.

C. DEVICES USING THE IMPROVED HOOK COLLECTOR Y The improved hook collector ofthe present invention has advantages that make possible its Vuse lin new types of transistors. Due tov the factrthat* it is produced by alloying a separately produced alloy pellet onto a'body of base material, it is possible to place the hook `co1- lector at any preferred location on the body. Thus, the body may be a thin, flat piece lof material, and the hook collector may be formed `on-one'face of the at material.

Thismakes possibleseveral newY types of transistors, as will now be explained. Y

One lsuch new type of transistor .is illustrated in Figs. 4 and 5, where 11 indicates the button of alloy, and The irst diffu-sion layer 13 and the second diffusion layerV 14 Vconstitute the hook collector as described above. Since the hook collector is located on top Vof body 10, it is possi-bleto locate a point contact emitter 16 on the same surface with, and to one side of, the' hook collector, as clearly shown in Figs. 4 and5. YVAfpiece of electrically conductive 'material 17 is attached to the opposite side material V17 to form thefbase connection. y

In 'the operation of the device of Figs. 4 and 5, holes carry current from the hook collector through theV body 1 0 of base material, to the base contact17. ThisV current carried by the holes is indicated by 'theyheavy ldot-dash lines 19 of Fig. 4. Y f,

A current of electrons ows from the ernitter16, some of whcihflow through the 2nd diffusion layer14 of the hook'collectonwhere they act as a control for the current 19. Others of these electrons will ow to the base contact 17.V This electron currentis indicated by the light'dash'lines 20 of Fig, 4. Y i

The arrangement 'of transistorv parts 'described above is of particular benefit, since it is de sirableto keep V.the

Y hole current 19 from going to the emitter, landlthis result is substantially accomplished by locating the. point contact emitter on the same surface With,A and tofoneY and germanium-silicon alloys, is not Vas rapid as kin germanium. Arsenic has 'and therefore it can be used in Vrelatively small amounts.

In the main example given above the pellet 11 consists ofv 99.9% Vindium and 0.1% arsenic. In the example given in the last section the alloy included 1% of galliurn and 1/2% of arsenic, vbalance lead.

Antirnony has a Llower segregation coefficient, and therefore it should 'be present in larger amounts. For example, a'suitable alloy would `consist of 1% gallium, 3% antimony, balance lead.

in connection with all of the percentages mentioned above it should be noted that the figures given depend Very largely on the temperature at which the pellet is to be alloyed :to the main body, as theval-ues used in determining the composition of the alloys are very sensitive to temperature and, to a Ilesser extent, to the relsistivity of the base material.

able semi-conductive material having N-type properties.

`These materials include germanium, silicon, or germanium-silicon alloys, ydope'd'with an N-type impurity. '1n of the alloy pellet would be an N-type material;Y

a relatively high segregationY coefficient,

side of the collector. vThis arrangement 4helps to make the device Vshort-circuit stable. Y v i Another arrangement of transistor partsfisshowngin Figs. 6 and 7, which involves the use oftwofcomb-like structures.. One of these combs, 21,;represents an alloy,V

hook'collector-formed Vby the method of` this invention,

and the other comb, 22, represents an emitter alloyed `to the body 10. These two combs are interleaved and are located on theV same surface of a Abody 10.0f base material. A piece of electrically conductive materialjZS is attached to the opposite side of the body 10 to form a base connection. The collector lead is shown at 24, the emitter lead at 25 and the base lead at 26.:Y f;

The comb-like collector body 21 maybe stamped out of a piece of the desired alloy, and alloyed to the body 10 by the method described above to produce an alloy hook collector. The emitter comb 22Y may tbe stamped from a piece of material suitable for-an emitter and alloyed to body 10.

An alternateV method of'producing the combs 20.?anrl v 21 is to evaporate the proper materials in the desired patterns onthe surface of body 10, and to subject the resulting combs to alloying processes as described'above.

Some ofthe advantages of the combtype arrangement of Fig. 6 vbecome apparent from Fig. 7, which is a dia'- grammatic cross Asection through one finger 21 `of the collector comb and through two adjacent fingers 22 of I the emitter comb. This diagram illustrates thetheory` that there isa ow of holes carrying current from the .y Y

hook collectornzlithrough the body l10 of ibase-" material to the base contact '23. 'Ihis :flow is .indicated by the heavy dot-dash lines 19.

There is also a ilow of electrons from the emitters 22, some of the electrons going to the base contact 23, and some flowing from each of the emitters through the layer 1li of the hook collector to control the current 19. This electron flow is indicated by the light dash lines 20.

lt has previously been proposed to use inter-leaved comb-type collectors and emitters, but in the absence of the alloy hook collector of the present invention, the current 19 owing from the collector to the base contact was not possible. The presence of this current gives a tremendous increase in power gain. Thus, Where the previously proposed structure would give a power gain of l0, the improved structure using the new alloy hook collector gives a power gain of 1,000.

Fig. 8 illustrates another arrangement in which a large alloy hook collector is alloyed to the surface of the body 1u, yand emitters 16 are placed on opposite sides of the hook collector. ln this case electron vilow 20 from one emitter ows into the 2nd diffusion -14 layer from one side of the hook collector, and electron ow 20 from the other emitter flows into the 2nd diffusion layer v14 from the opposite side. In this case the ow 19 is under 'partial control of each of the emitters. The use of two emitters to control a single collector is useful in devices such as phase measuring devices.

The term large when used in connection 'with Fig. 8 means that the alloy hook collector `is substantially larger than those used in the devices of Figs. l to 4 inclusive. In technical terms the word large as used to describe the alloy hook collector of Fig. 8 means large enough to permit the establishment of a potential diierence between one edge of the hook collector region and the other edge. If the resistance of the hook region is very high, such as one million ohms per square, large might be l mm. diameter for the alloy button. If the resistance is low, say 10,000 ohms per square, large may be 2 om. diameter of the button.

Fig. l0 illustrates the application of the invention to form a semi-conductor rectifier.

A known type of semi-conductor rectifier is shown in Fig. 9, where 10 represents a body of P-type base material, is an emitter of suitable N-type material, and 17 is a collector lead to which a conductor 18 is attached. In this type of rectifier it is desirable to keep the base region thin so that there will be little contribution Vto the forward resistance of the rectiier due to bulk resistivity of the base region. However, the material used to make the collector contact 17, e. g. tin, may cause a high recombination rate at the collector contact, giving a large supply of minority carriers which may diffuse through body 10 to the emitter 15, under reverse polarity, contributing to the leakage current. This will decrease the rectiiication ratio.

Fig. l0 illustrates the application to this type rectiiier of a hook collector according to the present invention. The hook collector, consisting of the first diffusion layer 13 and the second diffusion layer 14, is located between the collector contact 17 and the body 10 of base material.A With this construction some of the minority carriers (electrons) from base 10 will travel to the hook region, under reverse polarity for the'rectier, and will be collected by the hook, instead of contributing to the saturation current. Also, electrons which are contributed by regeneration at the collector contact will not reach the emitter 15, because they are impeded by a'potential barrier at the hook. For these reasons the leakage current is reduced, and the rectication ratio is increased.

As a specific example of possible materials, in Fig. l0 the main body 10 may be formed of P-type silicon, and the Contact 17 may be of lead containing small amounts of aluminum and lithium. Since aluminum is .a slow-ditiusing P-type material, the first dilusion layer 13 will be P-type because of the inuence of aluminum in this layer. Lithium, being a fast-diffusing N-type material, will cause the second diffusion layer to be N-type. The conductor 1S may be of molybdenum.

n the device illustrated in Fig. ll, the lower part is similar to the lower part of Fig. 10 in that a hook collector comprising diffusion layers 13 and 14 is located between the collector contact 17 and the body 10. However, the upper part of Fig. ll includes alternate emitters 27 and base elements 28. These emitters 27 and base elements 2S are preferably iformed of two Vinterleaved combs as in Fig. 6. The upper part of Fig. 1l represents a cross-section through the lingers of the combs as in the upper part of Fig. 7.

in Pig. ll the emitters 27 may be formed of lead doped with an N-type impurity, such as antimony. The base elements 28 may beformedfof lead doped with a P-type impurity, such as indium. rl`he elements 27 and 23 are alloyed to body v10. The diffusion layers 13 and 1-5 may be formed by usingan alloy of 95% aluminum and 5% lithium and the body 10 may be formed of silicon or of silicon-germanium alloy, preferably doped with a P-type impurity. The-diffusion layers are formed in the manner described above.

ln the construction of Fig. ll the base and emitter connections are on the same Vside of the body 1d, and since only small voltages are applied from base to emitter, these elements may be placed close to each other with little possibility of surface leakage. Moreover, there is a good ohmic connection from the base elements to the body 10.

CONCLUSlON The many advantages of the improved hook collector of this invention will be apparent to`those skilled in the art.

1t will of course be understood that the specic materials mentioned above are merely illustrative examples, and that any materials having similar properties may be substituted. According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim as my invention:

l. ln the method of producing a hook collector, the steps comprising applying a solid member comprising a slow diiusing P-type impurity and a fast diiusing N- type impurity to a solid body of a semi-conductor material having P-type semi-conductivity, the semi-conductor material being selected from Vthe group consisting of sil"- con, germanium and silicon-germanium alloys, the solid member containing the P-type impurity in such amounts as compared to the N-type impurity that when both are present in their respective amounts in the semi-conductor material the material will have P-type semi-conductivity, heating the assembly of the solid member and the solid body to a first temperature to cause the member to fuse and alloy with a part of the body of semi-conductor material, cooling the assembly to a mean temperature of the order of 20 C. below said iirst temperature and maintaining the assembly at the lower temperature so that the body of semiconductor material is slightly cooler than the molten alloy for a period of time to redeposit a thin layer of the semi-conductor material from the molten alloy upon the semi-conductor body and to diffuse the V`Ptype and N-type impurities into the body of semiconductor material thereby producing a uniformly thin iirst diusion layer adjacent the member wherein the type impurity predominates and imparts P-type semiconductivity to said first dilfusion layer, and producing V- 4 immediately beyond the first diffusion layer a second uniform and extremely thin second diffusion layer wherein the N-type impurity predominates and VVimparts: N-type semi-conductivity Vto-saidnsecond layer, and coolingV the assembly to Vroom temperature whereby aY unitary hook collector results.

V2. In the method of producing a hook collector, the steps comprising applying a solid member comprising a slow diffusing N-type impurity and a fast diffusing P-type impurity to a solid body of a semi-conductor material having VN-type semi-conductivity, the semi-conductor material being selected from the groupcon'sisting of silicon, germanium and silicon-germanium alloys,r the solid member containing the N-type impurity in such amount as Compared tothe P-type impurity that when both are present in their respective amounts in the semi-conductor material the material will have N-type semi-conductivity,

' -heating the assembly of the solid member and the solid body to Va iirst temperature to cause the member tofuse and alloy with a ypart of the body of semi-conductorrrnateriaL cooling the assembly to a mean temperature of theY order of 20 C. below said iirst temperature'and maintaining the assembly at the lower temperature so that the body of semiconductor material isY slightly cooler than themolten alloy for a period of time to redeposit a thin layer of the semi-conductor material fromthe molten Y also having the same Vconductivity asrthe first diffusion alloy upon the semi-conductor body and to diffuse the impurity predominates and imparts P-type .semi-conductivity to said second layer, and cooling the assembly to room temperature whereby a unitary hook collector member results, f

3. In the method of producing la hook collector, the steps comprising applying asolid member comprising a rst slow diffusing doping impurity and a second faster diffusing doping impurity toY a solid body of semi-conductor material suitable for preparing transistors there- Y from and alloyable with 'the solid member, the semi-conductor material being selected from the group Vconsisting f of silicon, germanium and silicon-germanium alloys, and having a semi-conductivity corresponding to that producible by Ythe first doping impurity, the solid member containing the iirst type of doping impurity in V'such amount as compared to the quantity-,of the second type of doping impurity that when both are present in their respective proportions in the semi-conductor material the material will have the semi-conductivity conferred by the first type of impurity, heating the assembly of solid member and solid body to a first temperature to cause the memberrto fuse and to dissolve and alloy withY some of i layer, and coolingfthe assembly to room'temperature V,whereby a unitary hook collector member results.V

4. vThe method of producing varhook` collector which comprisesi Vproviding a-piece of alloy containing a small percentage of lithium 'togetherwithra higher percentage .Y

of a slower diffusing P-type doping material, placing'the alloy piece on a body of silicon having P-type conductivity to form an assembly, heating the assembly to a first temperature to cause the piece tofuse Vand to alloy'with a part of the silicon inthe body, coolingthe assembly to a mean temperature ofthe order of 20 C. below said rst temperature, the body being maintained at a slightly lower temperature than the fused piece so that some of the silicon redeposits from the-fused piece as a thin layer on the body, and holding the assembly at'such lower temperature for a diffusion period during which the lithium and theV P-typeV doping material diffuse into the body of silicon, the P-type doping material ofthe alloy predomiv nating in a rstguniformly thin diffusion layer to Yir'rlpart Y to said first vdiifusion layer P-type conductivity, and the lithium diffusing'farther into the body to form av second uniform and extremely kthin 4diffusion layer in which it lpredorninaitesand accordingly said second diffusion layer having N-type conductivity, theV two diffusion layers being Y usable as a hook collector. 'Y Y 5. The method of producing a hook collector which comprises: providing a piece of alloy containing) a small percentage 'of lithium, the-balance being aluminum, placing the alloy'piecev on a body of silicon having P-type conductivity to forman assembly, heating the assembly to a first temperature Vto cause'the piece to melt and to` alloy with some of the silicon'in the body, cooling theassembly to a mean temperature of Vthe order of 20 C.-below Y said first temperature, the body being maintained'ataY slightly lower` temperature than the A'fused piece so'that some of the` siliconV redepositsV from the fused piece as a.

thin layeron Vthe body, and holding the assembly at such lower temperature fora diffusion period during which the lithium and the aluminum diffuse into the body of silicon,

the aluminum predominatingin a iirst-uniformlyvthin largetproportion of Va slow diffusing P-type dopingim-Y purity selected VVfromthe group consisting of aluminump galliurn and indium and a small proportion of a rapid diffusing N-type doping impurity selected from'the group the semi-conductor material, cooling the assembly to a mean temperature of the order of 20 C, lower than said first temperature while maintaining a gradient so that the Y solid vbody of semi-conductor is at a lower temperature p than themolten member so Vthat a layer of the semi- Y Y conductor material redeposits from the molten member, frnaintaining theY assembly at the lower temperature for terial, and producing immediately-beyond the first diffusion layer a second .uniform and extremely thin'diffusion layer in which the faster diffusing impurity predominates thereby imparting to said second diffusion layer vthe opposite typeV of conductivity, the'k redeposited layer.

` loy, whereby a thin layer of germanium redeposits on theV` consisting vof antimony, lithium andrarsenic, placing the alloy piece ona body of germanium having P-typecon-V a first temperature of about 570 C. to cause thepiece Y,

of the alloy to fuse to and dissolve and alloy with apart ofthe Ygermanium Vbody, cooling the assembly to a mean temperature of the order of 20 C. lower than said` rst temperature, 'while maintaininga gradient so thatthe body of germanium is slightly cooler than the'molten albody of germanium, and holding the assembly at VVsuch v.lower temperature'forY a diffusion vperiod during which the P-type and N-type impurities'diffuse into the body,-

and the P-type impurity predominates in a rst uniformly thin diiusion layer, said first layer accordingly having" P-type' conductivity, and the N-type impurity diffuses farther into the germanium'body toforma second uniformfand extremely thin diffusion layer kin, which it pre- "dominates,` saidV second layer accordingly having N-type conductivity, these two diffusion layers forming Vahooli Vcollector. 'Y Y .Y

The method of, producing a hoolcrcollectorn which comprises: providing a piece comprising an alloy of indium With about 0.1% of arsenic, placing the piece of alloy on a body of germanium having P-type conductivity to form an assembly, heating the assembly to a temperature of about 570 C. to cause the piece of alloy to fuse and to alloy with some of the germanium body, cooling the assembly to a mean temperature of about 550 C. while subjecting the assembly to a gradient cooling during which the liquid alloy is Slightly hotter than the body of germanium so that a thin layer or" germanium redeposits on the body, and holding the assembly at the lower temperature for a diffusion period of the order of 1/2 to 1 hour during which the indium and arsenic diffuse into the body, and the indium predominates in a rst uniformly thin diiusion layer, said first layer accordingly having P-type conductivity and the arsenic diuses farther into the germanium body to form a second uniform and eX- tremely thin diffusion layer in Which it predominates, said second layer accordingly having N-type conductivity, these two diffusion layers forming a hook collector.

Preferences Cited in the le of this patent UNITED STATES PATENTS 2,428,992 Ransley Oct. 14, 1947 2,449,484 Jaiee Sept. 14, 1948 2,567,970 Scali Sept. 18, 1951 2,569,347 Shockley Sept. 25, 1951 2,629,672 Sparks Feb. 24, 1953 2,637,770 Lark-Horovitz May 5, 1953 2,644,852 Dunlap July 7, 1953 2,701,326 Pfann Feb. 1, 1955 2,725,315 Fuller Nov. 29, 1955 FOREIGN PATENTS 510,303 Belgium Apr. 15, 1952 

1. IN THE METHOD OF PRODUCING A HOOK COLLECTOR, THE STEPS COMPRISING APPLYING A SOLID MEMBER COMPRISING A SLOW DIFFUSING P-TYPE IMPURITY AND A FAST DIFFUSING NTYPE IMPURITY TO A SOLID BODY OF A SEMI-CONDUCTOR MATERIAL HAVING P-TYPE SEMI-CONDUCTIVITY, THE SEMI-CONDUCTOR MATERIAL BEING SELECTED FROM THE ROUP CONSISTING OF SILICON, GERMANIUM AND SILICON-GERMANIUM ALLOYS, THE SOLID MEMBER CONTAINING THE P-TYPE IMPURITY IN SUCH AMOUNTS AS COMPARED TO THE N-TYPE IMPURITY THAT WHEN BOTH ARE PRESENT IN THEIR RESPECTIVE AMOUNTS IN THE SEMI-CONDUCTIVITY, MATERIAL THE MATERIAL WILL HAVE P-TYPE SEMI-CONDUCTIVITY HEATING THE ASSEMBLY OF THE SOLID MEMBER AND THE SOLID BODY TO A FIRST TEMPERATURE TO CAUSE THE MEMBER TO FUSE AND ALLOY WITH A PART OF THE BODY OF SEMI-CONDUCTOR MATERIAL, COOLING THE ASEMBLY TO A MEANS TEMPERATURE OF THE ORDER OF 20*C. BELOW SAID FIRST TEMPERATURE AND MAINTAINING THE ASSEMBLY AT THE LOWER TEMPERATURE SO THAT THE BODY OF SEMICONDUCTOR MATERIAL IS SLIGHTLY COOLER THAN THE MOLTEN ALLOY FOR A PERIOD OF TIME TO REDEPOSIT A THIN LAYER OF THE SEMI-CONDUCTOR MATERIAL FROM THE MOLTEN ALLOY UPON THE SEMI-CONDUCTOR BODY AND TO DIFFUSE THE P-TYPE AND N-TYPE IMPURITIES INTO THE BODY OF SEMICONDUCTOR MATERIAL THEREBY PRODUCING A UNIFORMLY THIN FIRST DIFFUSION LAYER ADJACENT THE MEMBER WHEREIN THE PTYPE IMPURITY PREDOMINATES AND IMPARTS P-TYPE SEMICONDUCTIVITY TO SAID FIRST DIFFUSION LAYER, AND PRODUCING IMMEDIATELY BEYOND THE FIRST DIFFUSION LAYER A SECOND UNIFORM AND EXTREMELY THIN SECOND DIFFUSION LAYER WHEREIN THE N-TYPE IMPURITY PREDOMINATES AND IMPARTS N-TYPE SEMI-CONDUCTIVITY TO SAID SECOND LAYER, AND COOLING THE ASSEMBLY TO ROOM TEMPERATURE WHEREBY A UNITARY HOOK COLLECTOR RESULTS. 